Several types of bone screws are known, in particular for osteosynthesis, which combine two or more of the following characteristics:                1. with or without a head;        2. threaded over the entire length of the screw body or over only a portion of this body;        3. having a thread with a constant pitch or a larger pitch in the distal portion; in this second case, the screw enables the reduction of a fracture through which it is implanted, the rotation of the screw moving the distal bone fragment towards the proximal bone fragment, taking into consideration the difference in pitch; and        4. having a thread with a constant diameter or a diameter becoming increasingly larger from the distal end to the proximal end.        
Existing screws do not give complete satisfaction as concerns carrying out an osteosynthesis, and this invention has the objective of remedying this disadvantage.